Commit 73bbf3b0 authored by Nikunj A Dadhania's avatar Nikunj A Dadhania Committed by Borislav Petkov (AMD)
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x86/tsc: Init the TSC for Secure TSC guests 

Use the GUEST_TSC_FREQ MSR to discover the TSC frequency instead of
relying on kvm-clock based frequency calibration.  Override both CPU and
TSC frequency calibration callbacks with securetsc_get_tsc_khz(). Since
the difference between CPU base and TSC frequency does not apply in this
case, the same callback is being used.

  [ bp: Carve out from
    https://lore.kernel.org/r/20250106124633.1418972-11-nikunj@amd.com

 ]

Signed-off-by: default avatarNikunj A Dadhania <nikunj@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250106124633.1418972-11-nikunj@amd.com
parent 0a2a98f6

arch/x86/coco/sev/core.c

+21 −0
Original line number Diff line number Diff line
@@ -103,6 +103,7 @@ static u64 secrets_pa __ro_after_init; 
 */

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;



/* #VC handler runtime per-CPU data */

struct sev_es_runtime_data {
@@ -3278,3 +3279,23 @@ void __init snp_secure_tsc_prepare(void) 


	pr_debug("SecureTSC enabled");

}



static unsigned long securetsc_get_tsc_khz(void)

{

	return snp_tsc_freq_khz;

}



void __init snp_secure_tsc_init(void)

{

	unsigned long long tsc_freq_mhz;



	if (!cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))

		return;



	setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);

	rdmsrl(MSR_AMD64_GUEST_TSC_FREQ, tsc_freq_mhz);

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



	x86_platform.calibrate_cpu = securetsc_get_tsc_khz;

	x86_platform.calibrate_tsc = securetsc_get_tsc_khz;

}

arch/x86/include/asm/sev.h

+2 −0
Original line number Diff line number Diff line
@@ -482,6 +482,7 @@ int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req 
			   struct snp_guest_request_ioctl *rio);



void __init snp_secure_tsc_prepare(void);

void __init snp_secure_tsc_init(void);



#else	/* !CONFIG_AMD_MEM_ENCRYPT */
@@ -524,6 +525,7 @@ static inline void snp_msg_free(struct snp_msg_desc *mdesc) { } 
static inline int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req,

					 struct snp_guest_request_ioctl *rio) { return -ENODEV; }

static inline void __init snp_secure_tsc_prepare(void) { }

static inline void __init snp_secure_tsc_init(void) { }



#endif	/* CONFIG_AMD_MEM_ENCRYPT */

arch/x86/kernel/tsc.c

+4 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ 
#include <asm/i8259.h>

#include <asm/topology.h>

#include <asm/uv/uv.h>

#include <asm/sev.h>



unsigned int __read_mostly cpu_khz;	/* TSC clocks / usec, not used here */

EXPORT_SYMBOL(cpu_khz);
@@ -1515,6 +1516,9 @@ void __init tsc_early_init(void) 
	/* Don't change UV TSC multi-chassis synchronization */

	if (is_early_uv_system())

		return;



	snp_secure_tsc_init();



	if (!determine_cpu_tsc_frequencies(true))

		return;

	tsc_enable_sched_clock();