Commit 94b36bc2 authored by Brijesh Singh's avatar Brijesh Singh Committed by Borislav Petkov (AMD)
Browse files

x86/sev: Add RMP entry lookup helpers 



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: default avatarBrijesh Singh <brijesh.singh@amd.com>
Co-developed-by: default avatarAshish Kalra <ashish.kalra@amd.com>
Signed-off-by: default avatarAshish Kalra <ashish.kalra@amd.com>
Signed-off-by: default avatarMichael Roth <michael.roth@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240126041126.1927228-7-michael.roth@amd.com
parent e3fd08af

arch/x86/include/asm/sev.h

+3 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/virt/svm/sev.c

+49 −0
Original line number Diff line number Diff line
@@ -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 @@ static int __init snp_rmptable_init(void) 
 * 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);