Commit 5fc2e891 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86_urgent_for_v6.16_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 fix from Borislav Petkov:

 - Make sure AMD SEV guests using secure TSC, include a TSC_FACTOR which
   prevents their TSCs from going skewed from the hypervisor's

* tag 'x86_urgent_for_v6.16_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/sev: Use TSC_FACTOR for Secure TSC frequency calculation
parents 463b1b2a 52e1a03e

arch/x86/coco/sev/core.c

+19 −3
Original line number Diff line number Diff line
@@ -88,7 +88,7 @@ static const char * const sev_status_feat_names[] = { 
 */

static u64 snp_tsc_scale __ro_after_init;

static u64 snp_tsc_offset __ro_after_init;

static u64 snp_tsc_freq_khz __ro_after_init;

static unsigned long snp_tsc_freq_khz __ro_after_init;



DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);

DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa);
@@ -2167,15 +2167,31 @@ static unsigned long securetsc_get_tsc_khz(void) 


void __init snp_secure_tsc_init(void)

{

	unsigned long long tsc_freq_mhz;

	struct snp_secrets_page *secrets;

	unsigned long tsc_freq_mhz;

	void *mem;



	if (!cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))

		return;



	mem = early_memremap_encrypted(sev_secrets_pa, PAGE_SIZE);

	if (!mem) {

		pr_err("Unable to get TSC_FACTOR: failed to map the SNP secrets page.\n");

		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SECURE_TSC);

	}



	secrets = (__force struct snp_secrets_page *)mem;



	setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);

	rdmsrq(MSR_AMD64_GUEST_TSC_FREQ, tsc_freq_mhz);

	snp_tsc_freq_khz = (unsigned long)(tsc_freq_mhz * 1000);



	/* Extract the GUEST TSC MHZ from BIT[17:0], rest is reserved space */

	tsc_freq_mhz &= GENMASK_ULL(17, 0);



	snp_tsc_freq_khz = SNP_SCALE_TSC_FREQ(tsc_freq_mhz * 1000, secrets->tsc_factor);



	x86_platform.calibrate_cpu = securetsc_get_tsc_khz;

	x86_platform.calibrate_tsc = securetsc_get_tsc_khz;



	early_memunmap(mem, PAGE_SIZE);

}

arch/x86/include/asm/sev.h

+16 −1
Original line number Diff line number Diff line
@@ -223,6 +223,18 @@ struct snp_tsc_info_resp { 
	u8 rsvd2[100];

} __packed;



/*

 * Obtain the mean TSC frequency by decreasing the nominal TSC frequency with

 * TSC_FACTOR as documented in the SNP Firmware ABI specification:

 *

 * GUEST_TSC_FREQ * (1 - (TSC_FACTOR * 0.00001))

 *

 * which is equivalent to:

 *

 * GUEST_TSC_FREQ -= (GUEST_TSC_FREQ * TSC_FACTOR) / 100000;

 */

#define SNP_SCALE_TSC_FREQ(freq, factor) ((freq) - (freq) * (factor) / 100000)



struct snp_guest_req {

	void *req_buf;

	size_t req_sz;
@@ -282,8 +294,11 @@ struct snp_secrets_page { 
	u8 svsm_guest_vmpl;

	u8 rsvd3[3];



	/* The percentage decrease from nominal to mean TSC frequency. */

	u32 tsc_factor;



	/* Remainder of page */

	u8 rsvd4[3744];

	u8 rsvd4[3740];

} __packed;



struct snp_msg_desc {