| Message ID | 20220128171804.569796-19-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
| Series | Add AMD Secure Nested Paging (SEV-SNP) Guest Support | expand |
On Fri, Jan 28, 2022 at 11:17:39AM -0600, Brijesh Singh wrote: > @@ -197,11 +198,21 @@ static int __init romchecksum(const unsigned char *rom, unsigned long length) > > void __init probe_roms(void) > { > - const unsigned char *rom; > unsigned long start, length, upper; > + const unsigned char *rom; > unsigned char c; > int i; > > + /* > + * The ROM memory is not part of the E820 system RAM and is not pre-validated > + * by the BIOS. The kernel page table maps the ROM region as encrypted memory, > + * the SEV-SNP requires the encrypted memory must be validated before the > + * access. Validate the ROM before accessing it. > + */ Lemme massage it: /* * The ROM memory range is not part of the e820 table and is therefore not * pre-validated by BIOS. The kernel page table maps the ROM region as encrypted * memory, and SEV-SNP requires encrypted memory to be validated before access. * Do that here. */
diff --git a/arch/x86/kernel/probe_roms.c b/arch/x86/kernel/probe_roms.c index 36e84d904260..d19a80565252 100644 --- a/arch/x86/kernel/probe_roms.c +++ b/arch/x86/kernel/probe_roms.c @@ -21,6 +21,7 @@ #include <asm/sections.h> #include <asm/io.h> #include <asm/setup_arch.h> +#include <asm/sev.h> static struct resource system_rom_resource = { .name = "System ROM", @@ -197,11 +198,21 @@ static int __init romchecksum(const unsigned char *rom, unsigned long length) void __init probe_roms(void) { - const unsigned char *rom; unsigned long start, length, upper; + const unsigned char *rom; unsigned char c; int i; + /* + * The ROM memory is not part of the E820 system RAM and is not pre-validated + * by the BIOS. The kernel page table maps the ROM region as encrypted memory, + * the SEV-SNP requires the encrypted memory must be validated before the + * access. Validate the ROM before accessing it. + */ + snp_prep_memory(video_rom_resource.start, + ((system_rom_resource.end + 1) - video_rom_resource.start), + SNP_PAGE_STATE_PRIVATE); + /* video rom */ upper = adapter_rom_resources[0].start; for (start = video_rom_resource.start; start < upper; start += 2048) {
probe_roms() accesses the memory range (0xc0000 - 0x10000) to probe various ROMs. The memory range is not part of the E820 system RAM range. The memory range is mapped as private (i.e encrypted) in page table. When SEV-SNP is active, all the private memory must be validated before the access. The ROM range was not part of E820 map, so the guest BIOS did not validate it. An access to invalidated memory will cause a VC exception. The guest does not support handling not-validated VC exception yet, so validate the ROM memory regions before it is accessed. Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> --- arch/x86/kernel/probe_roms.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)