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x86/pv: Store the data segment selectors outside of cpu_user_regs

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In order to support FRED, we're going to have to remove the {ds..gs} fields
from struct cpu_user_regs.  This will impact v->arch.user_regs.

These fields are unused for HVM guests, but for PV hold the selector values
when the vCPU is scheduled out.

Introduce new fields for the selectors in struct pv_vcpu, and update:

 * {save,load}_segments(), context switching
 * arch_{set,set}_info_guest(), hypercalls
 * vcpu_show_registers(), diagnostics
 * dom0_construct(), PV dom0

to use the new storage.  This removes the final user of read_sregs() so drop
it too.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
This commit is contained in:
Andrew Cooper committed 2025-08-08 13:23:11 +01:00
1 parent 9f892f84c2
commit 68ae02120a
6 files changed
+53 -57
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xen/arch/x86/domain.c
+35 -35
View File
@@ -1247,10 +1247,10 @@ int arch_set_info_guest(
v->arch.user_regs.rflags = c.nat->user_regs.rflags;
v->arch.user_regs.rsp = c.nat->user_regs.rsp;
v->arch.user_regs.ss = c.nat->user_regs.ss;
v->arch.user_regs.es = c.nat->user_regs.es;
v->arch.user_regs.ds = c.nat->user_regs.ds;
v->arch.user_regs.fs = c.nat->user_regs.fs;
v->arch.user_regs.gs = c.nat->user_regs.gs;
v->arch.pv.es = c.nat->user_regs.es;
v->arch.pv.ds = c.nat->user_regs.ds;
v->arch.pv.fs = c.nat->user_regs.fs;
v->arch.pv.gs = c.nat->user_regs.gs;
if ( is_pv_domain(d) )
memcpy(v->arch.pv.trap_ctxt, c.nat->trap_ctxt,
@@ -1271,10 +1271,10 @@ int arch_set_info_guest(
v->arch.user_regs.eflags = c.cmp->user_regs.eflags;
v->arch.user_regs.esp = c.cmp->user_regs.esp;
v->arch.user_regs.ss = c.cmp->user_regs.ss;
v->arch.user_regs.es = c.cmp->user_regs.es;
v->arch.user_regs.ds = c.cmp->user_regs.ds;
v->arch.user_regs.fs = c.cmp->user_regs.fs;
v->arch.user_regs.gs = c.cmp->user_regs.gs;
v->arch.pv.es = c.cmp->user_regs.es;
v->arch.pv.ds = c.cmp->user_regs.ds;
v->arch.pv.fs = c.cmp->user_regs.fs;
v->arch.pv.gs = c.cmp->user_regs.gs;
if ( is_pv_domain(d) )
{
@@ -1762,7 +1762,6 @@ long do_vcpu_op(int cmd, unsigned int vcpuid, XEN_GUEST_HANDLE_PARAM(void) arg)
*/
static void load_segments(struct vcpu *n)
{
struct cpu_user_regs *uregs = &n->arch.user_regs;
unsigned long gsb = 0, gss = 0;
bool compat = is_pv_32bit_vcpu(n);
bool all_segs_okay = true, fs_gs_done = false;
@@ -1796,7 +1795,7 @@ static void load_segments(struct vcpu *n)
if ( !(n->arch.flags & TF_kernel_mode) )
SWAP(gsb, gss);
if ( using_svm() && (uregs->fs | uregs->gs) <= 3 )
if ( using_svm() && (n->arch.pv.fs | n->arch.pv.gs) <= 3 )
fs_gs_done = svm_load_segs(n->arch.pv.ldt_ents, LDT_VIRT_START(n),
n->arch.pv.fs_base, gsb, gss);
}
@@ -1805,12 +1804,12 @@ static void load_segments(struct vcpu *n)
{
load_LDT(n);
TRY_LOAD_SEG(fs, uregs->fs);
TRY_LOAD_SEG(gs, uregs->gs);
TRY_LOAD_SEG(fs, n->arch.pv.fs);
TRY_LOAD_SEG(gs, n->arch.pv.gs);
}
TRY_LOAD_SEG(ds, uregs->ds);
TRY_LOAD_SEG(es, uregs->es);
TRY_LOAD_SEG(ds, n->arch.pv.ds);
TRY_LOAD_SEG(es, n->arch.pv.es);
if ( !fs_gs_done && !compat )
{
@@ -1863,13 +1862,13 @@ static void load_segments(struct vcpu *n)
}
if ( ret |
put_guest(rflags, esp - 1) |
put_guest(cs_and_mask, esp - 2) |
put_guest(regs->eip, esp - 3) |
put_guest(uregs->gs, esp - 4) |
put_guest(uregs->fs, esp - 5) |
put_guest(uregs->es, esp - 6) |
put_guest(uregs->ds, esp - 7) )
put_guest(rflags, esp - 1) |
put_guest(cs_and_mask, esp - 2) |
put_guest(regs->eip, esp - 3) |
put_guest(n->arch.pv.gs, esp - 4) |
put_guest(n->arch.pv.fs, esp - 5) |
put_guest(n->arch.pv.es, esp - 6) |
put_guest(n->arch.pv.ds, esp - 7) )
domain_crash(n->domain,
"Error creating compat failsafe callback frame\n");
@@ -1895,17 +1894,17 @@ static void load_segments(struct vcpu *n)
cs_and_mask = (unsigned long)regs->cs |
((unsigned long)vcpu_info(n, evtchn_upcall_mask) << 32);
if ( put_guest(regs->ss, rsp - 1) |
put_guest(regs->rsp, rsp - 2) |
put_guest(rflags, rsp - 3) |
put_guest(cs_and_mask, rsp - 4) |
put_guest(regs->rip, rsp - 5) |
put_guest(uregs->gs, rsp - 6) |
put_guest(uregs->fs, rsp - 7) |
put_guest(uregs->es, rsp - 8) |
put_guest(uregs->ds, rsp - 9) |
put_guest(regs->r11, rsp - 10) |
put_guest(regs->rcx, rsp - 11) )
if ( put_guest(regs->ss, rsp - 1) |
put_guest(regs->rsp, rsp - 2) |
put_guest(rflags, rsp - 3) |
put_guest(cs_and_mask, rsp - 4) |
put_guest(regs->rip, rsp - 5) |
put_guest(n->arch.pv.gs, rsp - 6) |
put_guest(n->arch.pv.fs, rsp - 7) |
put_guest(n->arch.pv.es, rsp - 8) |
put_guest(n->arch.pv.ds, rsp - 9) |
put_guest(regs->r11, rsp - 10) |
put_guest(regs->rcx, rsp - 11) )
domain_crash(n->domain,
"Error creating failsafe callback frame\n");
@@ -1934,9 +1933,10 @@ static void load_segments(struct vcpu *n)
*/
static void save_segments(struct vcpu *v)
{
struct cpu_user_regs *regs = &v->arch.user_regs;
read_sregs(regs);
asm ( "mov %%ds, %0" : "=m" (v->arch.pv.ds) );
asm ( "mov %%es, %0" : "=m" (v->arch.pv.es) );
asm ( "mov %%fs, %0" : "=m" (v->arch.pv.fs) );
asm ( "mov %%gs, %0" : "=m" (v->arch.pv.gs) );
if ( !is_pv_32bit_vcpu(v) )
{
xen/arch/x86/domctl.c
+8 -8
View File
@@ -1412,10 +1412,10 @@ void arch_get_info_guest(struct vcpu *v, vcpu_guest_context_u c)
c.nat->user_regs.rflags = v->arch.user_regs.rflags;
c.nat->user_regs.rsp = v->arch.user_regs.rsp;
c.nat->user_regs.ss = v->arch.user_regs.ss;
c.nat->user_regs.es = v->arch.user_regs.es;
c.nat->user_regs.ds = v->arch.user_regs.ds;
c.nat->user_regs.fs = v->arch.user_regs.fs;
c.nat->user_regs.gs = v->arch.user_regs.gs;
c.nat->user_regs.es = v->arch.pv.es;
c.nat->user_regs.ds = v->arch.pv.ds;
c.nat->user_regs.fs = v->arch.pv.fs;
c.nat->user_regs.gs = v->arch.pv.gs;
if ( is_pv_domain(d) )
memcpy(c.nat->trap_ctxt, v->arch.pv.trap_ctxt,
@@ -1437,10 +1437,10 @@ void arch_get_info_guest(struct vcpu *v, vcpu_guest_context_u c)
c.cmp->user_regs.eflags = v->arch.user_regs.eflags;
c.cmp->user_regs.esp = v->arch.user_regs.esp;
c.cmp->user_regs.ss = v->arch.user_regs.ss;
c.cmp->user_regs.es = v->arch.user_regs.es;
c.cmp->user_regs.ds = v->arch.user_regs.ds;
c.cmp->user_regs.fs = v->arch.user_regs.fs;
c.cmp->user_regs.gs = v->arch.user_regs.gs;
c.cmp->user_regs.es = v->arch.pv.es;
c.cmp->user_regs.ds = v->arch.pv.ds;
c.cmp->user_regs.fs = v->arch.pv.fs;
c.cmp->user_regs.gs = v->arch.pv.gs;
if ( is_pv_domain(d) )
{
xen/arch/x86/include/asm/domain.h
+2
View File
@@ -546,6 +546,8 @@ struct pv_vcpu
bool syscall32_disables_events;
bool sysenter_disables_events;
uint16_t ds, es, fs, gs;
/*
* 64bit segment bases.
*
xen/arch/x86/include/asm/regs.h
-8
View File
@@ -44,12 +44,4 @@
__sel; \
})
static inline void read_sregs(struct cpu_user_regs *regs)
{
asm ( "mov %%ds, %0" : "=m" (regs->ds) );
asm ( "mov %%es, %0" : "=m" (regs->es) );
asm ( "mov %%fs, %0" : "=m" (regs->fs) );
asm ( "mov %%gs, %0" : "=m" (regs->gs) );
}
#endif /* __X86_REGS_H__ */
xen/arch/x86/pv/dom0_build.c
+4 -2
View File
@@ -1012,8 +1012,10 @@ static int __init dom0_construct(const struct boot_domain *bd)
* [rAX,rBX,rCX,rDX,rDI,rBP,R8-R15 are zero]
*/
regs = &v->arch.user_regs;
regs->ds = regs->es = regs->fs = regs->gs =
(compat ? FLAT_COMPAT_KERNEL_DS : FLAT_KERNEL_DS);
v->arch.pv.ds = (compat ? FLAT_COMPAT_KERNEL_DS : FLAT_KERNEL_DS);
v->arch.pv.es = (compat ? FLAT_COMPAT_KERNEL_DS : FLAT_KERNEL_DS);
v->arch.pv.fs = (compat ? FLAT_COMPAT_KERNEL_DS : FLAT_KERNEL_DS);
v->arch.pv.gs = (compat ? FLAT_COMPAT_KERNEL_DS : FLAT_KERNEL_DS);
regs->ss = (compat ? FLAT_COMPAT_KERNEL_SS : FLAT_KERNEL_SS);
regs->cs = (compat ? FLAT_COMPAT_KERNEL_CS : FLAT_KERNEL_CS);
regs->rip = parms.virt_entry;
xen/arch/x86/x86_64/traps.c
+4 -4
View File
@@ -220,10 +220,10 @@ void vcpu_show_registers(struct vcpu *v)
state.gsb = gsb;
state.gss = gss;
state.ds = v->arch.user_regs.ds;
state.es = v->arch.user_regs.es;
state.fs = v->arch.user_regs.fs;
state.gs = v->arch.user_regs.gs;
state.ds = v->arch.pv.ds;
state.es = v->arch.pv.es;
state.fs = v->arch.pv.fs;
state.gs = v->arch.pv.gs;
context = CTXT_pv_guest;
}
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