x86/HVM: drop stdvga's "sr[]" struct member

No consumers are left, hence the producer and the array itself can also
go away. The static sr_mask[] is then orphaned and hence needs dropping,
too.

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 7aba44bdd7)

xen/arch/x86/hvm/stdvga.c

@@ -37,18 +37,6 @@
 #define VGA_MEM_BASE 0xa0000
 #define VGA_MEM_SIZE 0x20000
 
-/* force some bits to zero */
-static const uint8_t sr_mask[8] = {
-    (uint8_t)~0xfc,
-    (uint8_t)~0xc2,
-    (uint8_t)~0xf0,
-    (uint8_t)~0xc0,
-    (uint8_t)~0xf1,
-    (uint8_t)~0xff,
-    (uint8_t)~0xff,
-    (uint8_t)~0x00,
-};
-
 static int stdvga_outb(uint64_t addr, uint8_t val)
 {
     struct hvm_hw_stdvga *s = &current->domain->arch.hvm.stdvga;
@@ -60,12 +48,6 @@ static int stdvga_outb(uint64_t addr, uint8_t val)
         s->sr_index = val;
         break;
 
-    case 0x3c5:                 /* sequencer data register */
-        rc = (s->sr_index < sizeof(s->sr));
-        if ( rc )
-            s->sr[s->sr_index] = val & sr_mask[s->sr_index] ;
-        break;
-
     case 0x3ce:                 /* graphics address register */
         s->gr_index = val;
         break;

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

@@ -112,7 +112,6 @@ struct vpci_arch_msix_entry {
 
 struct hvm_hw_stdvga {
     uint8_t sr_index;
-    uint8_t sr[8];
     uint8_t gr_index;
     struct page_info *vram_page[64];  /* shadow of 0xa0000-0xaffff */
     spinlock_t lock;