Commit 7e5b662 fixed p2m_altp2m_get_or_propagate() to use the altp2m's
default_access when propagating entries from the host p2m. However, the same
fix was not applied to altp2m_get_effective_entry(), which has the same issue.
When altp2m_get_effective_entry() prepopulates a superpage from the host
p2m, it incorrectly uses the host p2m's access permissions instead of
the altp2m's default_access. This causes problems when the superpage is
later split (e.g., when setting mem_access on a specific 4K page): all
512 entries inherit the host p2m's access rights instead of the altp2m's
default_access.
This issue became apparent after commit 50baf2d, which causes the host p2m
to use superpages more frequently. Before that commit, the host p2m
typically had 4K entries after VM restore, so the prepopulate branch was
rarely taken.
Symptoms include memory-access events firing for unexpected pages when
using VMI tools with altp2m, particularly after VM resume.
The issue can be worked around by booting with "hap_1gb=0 hap_2mb=0".
Amends: 7e5b662b28 ("x86/altp2m: p2m_altp2m_get_or_propagate() should honor ap2m->default_access")
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
SMBIOS specification dictates that tables should have a minimal length.
This commit introduces further validation for user-input SMBIOS tables.
As per SMBIOS Reference Specification:
* Type 0: For version 2.3 and later implementations, the length is at least 14h
* Type 1: 1Bh for 2.4 and later
* Type 2: at least 08h
* Type 3: 0Dh for version 2.1 and later
* Type 11: 5h (+ strings)
* Type 22: 1Ah (+ strings)
* Type 39: a minimum of 10h
Notably, this also fixes previously incorrect check for chassis handle in
smbios_type_2_init. Chassis handle is a WORD, therefore, the condition now
correctly checks for >= 13 instead of > 13.
hvmloader currently implements version 2.4
Furthermore, this commit introduces smbios_pt_copy helper function to substitute
previously repeating pattern of locating the struct in physical memory (via
get_smbios_pt_struct), checking the length and copying it into SMBIOS region.
Fixes: 4d23036e70 ("HVM firmware passthrough SMBIOS processing")
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
* `sizeof_field` returns the size of a specific struct member
* `endof_field` returns the offset to the end of the member within the struct
It will be useful in upcoming layout checks of SMBIOS structs.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>
Allow developers using the OCaml bindings to set the altp2m_count parameter.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Christian Lindig <christian.lindig@cloud.com>
Since libxl finally sends the altp2m.nr value, we can remove the previously
introduced temporary workaround.
Creating domain with enabled altp2m while setting altp2m.nr == 0 doesn't
make sense and it's probably not what user wants.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
This commit activates the previously introduced altp2m_count parameter,
establishing the connection between libxl and Xen.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>
This commit introduces the ability to configure the maximum number of altp2m
views for the domain during its creation. Previously, the limits were hardcoded
to a maximum of 10. This change allows for greater flexibility in environments
that require more or fewer altp2m views.
The maximum configurable limit for nr_altp2m on x86 is now set to
MAX_NR_ALTP2M (which currently holds the MAX_EPTP value - 512). This cap is
linked to the architectural limit of the EPTP-switching VMFUNC, which supports
up to 512 entries. Despite there being no inherent need for limiting nr_altp2m
in scenarios not utilizing VMFUNC, decoupling these components would necessitate
substantial code changes.
xen_domctl_createdomain::altp2m is extended for a new field `nr`, that will
configure this limit for a domain. Additionally, previous altp2m.opts value
has been reduced from uint32_t to uint16_t so that both of these fields occupy
as little space as possible.
Accesses to the altp2m_p2m array are modified to respect the new nr_altp2m
value. Accesses to the altp2m_(visible_)eptp arrays are unmodified, since
these arrays always have fixed size of MAX_EPTP.
Additional sanitization is introduced in the x86/arch_sanitise_domain_config
to fix the altp2m.nr value to 10 if it is previously set to 0. This behavior
is only temporary and immediately removed in the upcoming commit (which will
disallow creating a domain with enabled altp2m with zero nr_altp2m).
The reason for this temporary workaround is to retain the legacy behavior
until the feature is fully activated in libxl.
Also, arm/arch_sanitise_domain_config is extended to not allow requesting
non-zero altp2ms.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com> # mem_access/mem_sharing
Acked-by: Julien Grall <jgrall@amazon.com>
This change consistently guards all altp2m-related functionality
behind #ifdef CONFIG_ALTP2M, so that code and data structures related
to alternate p2m views are only included when the feature is enabled.
Apart from that:
- hvmemul_vmfunc() returns X86EMUL_UNHANDLEABLE when altp2m is disabled.
- do_altp2m_op() returns EOPNOTSUPP when altp2m is disabled.
- struct hvm_vcpu, arch_domain, and hvm_function_table only define altp2m
fields when the feature is enabled.
- Moved several declarations under #ifdef CONFIG_ALTP2M in p2m.h to avoid
polluting builds that don't require the feature.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com> # mem_access
Remove the no-op stubs from the ARM, PPC, and RISC‑V p2m headers and stop
providing a stub in arch/x86/include/asm/p2m.h.
Declare p2m_altp2m_check() in xen/include/xen/p2m-common.h and gate all
call sites with CONFIG_ALTP2M:
- wrap the fast_single_step block in hvm/monitor.c with #ifdef CONFIG_ALTP2M
(IS_ENABLED(CONFIG_ALTP2M) is not used here, because in the subsequent commit
hvm_vcpu::fast_single_step will be guarded by CONFIG_ALTP2M)
- make the vm_event.c path conditional via IS_ENABLED(CONFIG_ALTP2M)
No functional change intended: on builds without ALTP2M the calls are
compiled out; on builds with ALTP2M behavior is unchanged.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com> # arm
Acked-by: Tamas K Lengyel <tamas@tklengyel.com> # vm_event/monitor
Wrap the p2m_is_altp2m() check with IS_ENABLED(CONFIG_ALTP2M) to allow the
compiler to short-circuit the condition at build time when ALTP2M is disabled.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Update manual pages to include detailed information about the altp2m_count
configuration parameter.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>
Introduce a new altp2m_count parameter to control the maximum number of altp2m
views a domain can use. By default, if altp2m_count is unspecified and altp2m
is enabled, the value is set to 10, reflecting the legacy behavior.
This change is preparatory; it establishes the groundwork for the feature but
does not activate it.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Nick Rosbrook <enr0n@ubuntu.com>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
Update manual pages to include detailed information about the altp2m_count
configuration parameter.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>
Introduce a new altp2m_count parameter to control the maximum number of altp2m
views a domain can use. By default, if altp2m_count is unspecified and altp2m
is enabled, the value is set to 10, reflecting the legacy behavior.
This change is preparatory; it establishes the groundwork for the feature but
does not activate it.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
Acked-by: Nick Rosbrook <enr0n@ubuntu.com>
Encapsulate the altp2m options within a struct. This change is preparatory
and sets the groundwork for introducing additional parameter in subsequent
commit.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Christian Lindig <christian.lindig@cloud.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>
Acked-by: Julien Grall <jgrall@amazon.com> # arm
Reviewed-by: Jan Beulich <jbeulich@suse.com> # hypervisor
This patch introduces a new XENMEM_access_r_pw permission.
Functionally, it is similar to XENMEM_access_r, but for processors
with TERTIARY_EXEC_EPT_PAGING_WRITE support (Intel 12th Gen/Alder Lake
and later, Xeon 4th Gen/Sappire Rapids and later), it also permits the
CPU to write to the page during guest page-table walks (e.g., updating
A/D bits) without triggering an EPT violation.
This behavior works by both enabling the EPT paging-write feature and
setting the EPT paging-write flag in the EPT leaf entry.
This feature provides a significant performance boost for
introspection tools that monitor guest page-table updates. Previously,
every page-table modification by the guest—including routine updates
like setting A/D bits—triggered an EPT violation, adding unnecessary
overhead. The new XENMEM_access_r_pw permission allows these
"uninteresting" updates to occur without EPT violations, improving
efficiency.
Additionally, this feature simplifies the handling of race conditions
in scenarios where an introspection tool:
- Sets an "invisible breakpoint" in the altp2m view for a function F.
- Monitors guest page-table updates to track whether the page
containing F is paged out.
- Encounters a cleared Access (A) bit on the page containing F while
the guest is about to execute the breakpoint.
In the current implementation:
- If xc_monitor_inguest_pagefault() is enabled, the introspection tool
must emulate both the breakpoint and the setting of the Access bit.
- If xc_monitor_inguest_pagefault() is disabled, Xen handles the EPT
violation without notifying the introspection tool, setting the
Access bit and emulating the instruction. However, Xen fetches the
instruction from the default view instead of the altp2m view,
potentially causing the breakpoint to be missed.
With this patch, setting XENMEM_access_r_pw for monitored guest
page-tables prevents EPT violations in these cases. This change
enhances performance and reduces complexity for introspection tools,
ensuring seamless breakpoint handling while tracking guest page-table
updates.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
The EPT Paging-write feature (when enabled by the
TERTIARY_EXEC_EPT_PAGING_WRITE bit) uses bit 58 of the EPT entry to
indicate that guest paging may update the page, even if the W access
is not set.
This patch is a preparation for the EPT Paging-write feature.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reorder the condition checks within the HVM_MONITOR_SINGLESTEP_BREAKPOINT
case to enable fast singlestepping independently of the singlestep monitor
being enabled. Previously, fast singlestepping required the singlestep
monitor to be explicitly enabled through xc_monitor_singlestep, even though
it operates entirely within Xen and does not generate external events.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
This patch addresses a behavior discrepancy in the handling of altp2m views,
where upon the creation and subsequent EPT violation, the page access
permissions were incorrectly inherited from the hostp2m instead of respecting
the altp2m default_access.
Previously, when a new altp2m view was established with restrictive
default_access permissions and activated via xc_altp2m_switch_to_view(),
it failed to trigger an event on the first access violation. This behavior
diverged from the intended mechanism, where the altp2m's default_access
should dictate the initial permissions, ensuring proper event triggering on
access violations.
The correction involves modifying the handling mechanism to respect the
altp2m view's default_access upon its activation, eliminating the need for
setting memory access permissions for the entire altp2m range (e.g. within
xen-access.c). This change not only aligns the behavior with the expected
access control logic but also results in a significant performance improvement
by reducing the overhead associated with setting memory access permissions
across the altp2m range.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
It's located in libxl_domain_build_info, not libxl_domain_create_info.
Fixes: 45ba9a7d76 ("tools/[lib]xl: Add vmtrace_buf_size parameter")
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
This patch addresses an issue where the fast singlestep setting would persist
despite xc_domain_debug_control being called with XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_OFF.
Specifically, if fast singlestep was enabled in a VMI session and that session
stopped before the MTF trap occurred, the fast singlestep setting remained
active even though MTF itself was disabled. This led to a situation where, upon
starting a new VMI session, the first event to trigger an EPT violation would
cause the corresponding EPT event callback to be skipped due to the lingering
fast singlestep setting.
The fix ensures that the fast singlestep setting is properly reset when
disabling single step debugging operations.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Reviewed-by: Tamas K Lengyel <tamas@tklengyel.com>
Add the missing `vmtrace_buf_kb` field to the OCaml bindings to match the
vm.cfg configuration, correcting an oversight from its initial introduction.
Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Christian Lindig <christian.lindig@cloud.com>
Petr Beneš