x86/HVM: drop stdvga's "{g,s}r_index" struct members

No consumers are left, hence the producer and the fields themselves can
also go away. stdvga_outb() is then useless, rendering stdvga_out()
useless as well. Hence the entire I/O port intercept can go away.

This is part of XSA-463 / CVE-2024-45818

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
(cherry picked from commit 86c03372e1)

xen/arch/x86/hvm/stdvga.c

@@ -38,62 +38,6 @@
 #define VGA_MEM_BASE 0xa0000
 #define VGA_MEM_SIZE 0x20000
 
-static int stdvga_outb(uint64_t addr, uint8_t val)
-{
-    struct hvm_hw_stdvga *s = &current->domain->arch.hvm.stdvga;
-    int rc = 1;
-
-    switch ( addr )
-    {
-    case 0x3c4:                 /* sequencer address register */
-        s->sr_index = val;
-        break;
-
-    case 0x3ce:                 /* graphics address register */
-        s->gr_index = val;
-        break;
-
-    default:
-        rc = 0;
-        break;
-    }
-
-    return rc;
-}
-
-static void stdvga_out(uint32_t port, uint32_t bytes, uint32_t val)
-{
-    switch ( bytes )
-    {
-    case 1:
-        stdvga_outb(port, val);
-        break;
-
-    case 2:
-        stdvga_outb(port + 0, val >> 0);
-        stdvga_outb(port + 1, val >> 8);
-        break;
-
-    default:
-        break;
-    }
-}
-
-static int cf_check stdvga_intercept_pio(
-    int dir, unsigned int port, unsigned int bytes, uint32_t *val)
-{
-    struct hvm_hw_stdvga *s = &current->domain->arch.hvm.stdvga;
-
-    if ( dir == IOREQ_WRITE )
-    {
-        spin_lock(&s->lock);
-        stdvga_out(port, bytes, *val);
-        spin_unlock(&s->lock);
-    }
-
-    return X86EMUL_UNHANDLEABLE; /* propagate to external ioemu */
-}
-
 static int cf_check stdvga_mem_read(
     const struct hvm_io_handler *handler, uint64_t addr, uint32_t size,
     uint64_t *p_data)
@@ -195,11 +139,6 @@ void stdvga_init(struct domain *d)
     {
         struct hvm_io_handler *handler;
 
-        /* Sequencer registers. */
-        register_portio_handler(d, 0x3c4, 2, stdvga_intercept_pio);
-        /* Graphics registers. */
-        register_portio_handler(d, 0x3ce, 2, stdvga_intercept_pio);
-
         /* VGA memory */
         handler = hvm_next_io_handler(d);
 

xen/arch/x86/include/asm/hvm/io.h

@@ -122,8 +122,6 @@ struct vpci_arch_msix_entry {
 };
 
 struct hvm_hw_stdvga {
-    uint8_t sr_index;
-    uint8_t gr_index;
     struct page_info *vram_page[64];  /* shadow of 0xa0000-0xaffff */
     spinlock_t lock;
 };