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x86/sev: Add RMP entry lookup helpers

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Add a helper that can be used to access information contained in the RMP
entry corresponding to a particular PFN. This will be needed to make
decisions on how to handle setting up mappings in the NPT in response to
guest page-faults and handling things like cleaning up pages and setting
them back to the default hypervisor-owned state when they are no longer
being used for private data.

  [ mdr: separate 'assigned' indicator from return code, and simplify
    function signatures for various helpers. ]

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240126041126.1927228-7-michael.roth@amd.com
This commit is contained in:
Brijesh Singh 2024-01-25 22:11:06 -06:00 committed by Borislav Petkov (AMD)
parent e3fd08afb7
commit 94b36bc244
2 changed files with 52 additions and 0 deletions
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3
arch/x86/include/asm/sev.h
View File

@ -90,6 +90,7 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs);
/* RMP page size */
#define RMP_PG_SIZE_4K 0
#define RMP_PG_SIZE_2M 1
#define RMP_TO_PG_LEVEL(level) (((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
#define RMPADJUST_VMSA_PAGE_BIT BIT(16)
@ -245,8 +246,10 @@ static inline u64 sev_get_status(void) { return 0; }
#ifdef CONFIG_KVM_AMD_SEV
bool snp_probe_rmptable_info(void);
int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level);
#else
static inline bool snp_probe_rmptable_info(void) { return false; }
static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; }
#endif
#endif

49
arch/x86/virt/svm/sev.c
View File

@ -53,6 +53,9 @@ struct rmpentry {
*/
#define RMPTABLE_CPU_BOOKKEEPING_SZ 0x4000
/* Mask to apply to a PFN to get the first PFN of a 2MB page */
#define PFN_PMD_MASK GENMASK_ULL(63, PMD_SHIFT - PAGE_SHIFT)
static u64 probed_rmp_base, probed_rmp_size;
static struct rmpentry *rmptable __ro_after_init;
static u64 rmptable_max_pfn __ro_after_init;
@ -214,3 +217,49 @@ nosnp:
* This must be called after the IOMMU has been initialized.
*/
device_initcall(snp_rmptable_init);
static struct rmpentry *get_rmpentry(u64 pfn)
{
if (WARN_ON_ONCE(pfn > rmptable_max_pfn))
return ERR_PTR(-EFAULT);
return &rmptable[pfn];
}
static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
{
struct rmpentry *large_entry, *entry;
if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
return ERR_PTR(-ENODEV);
entry = get_rmpentry(pfn);
if (IS_ERR(entry))
return entry;
/*
* Find the authoritative RMP entry for a PFN. This can be either a 4K
* RMP entry or a special large RMP entry that is authoritative for a
* whole 2M area.
*/
large_entry = get_rmpentry(pfn & PFN_PMD_MASK);
if (IS_ERR(large_entry))
return large_entry;
*level = RMP_TO_PG_LEVEL(large_entry->pagesize);
return entry;
}
int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
{
struct rmpentry *e;
e = __snp_lookup_rmpentry(pfn, level);
if (IS_ERR(e))
return PTR_ERR(e);
*assigned = !!e->assigned;
return 0;
}
EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);