Commit 959d3f75 authored by Tycho Andersen (AMD)'s avatar Tycho Andersen (AMD) Committed by Borislav Petkov (AMD)
Browse files

x86/virt/sev: Drop support for SNP hotplug 



During an SNP_INIT(_EX), the SEV firmware checks that all CPUs have the SNP
syscfg bit set, and fails if they do not. As such, it does not make
sense to have offline CPUs: the firmware will fail initialization because
of the offlined ones that the kernel did not initialize.

Further, there is a bug: during SNP_INIT(_EX) the firmware requires the MFDM
syscfg bit to be set in addition to having SNP enabled, which the previous
hotplug code did not do. Since k8_check_syscfg_dram_mod_en() enforces this
be cleared, hotplug wouldn't work.

Signed-off-by: default avatarTycho Andersen (AMD) <tycho@kernel.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Link: https://patch.msgid.link/20260309180053.2389118-2-tycho@kernel.org
parent 1f318b96

arch/x86/virt/svm/sev.c

+5 −27
Original line number Diff line number Diff line
@@ -130,33 +130,20 @@ static unsigned long snp_nr_leaked_pages; 
#undef pr_fmt

#define pr_fmt(fmt)	"SEV-SNP: " fmt



static int __mfd_enable(unsigned int cpu)

static __init void mfd_enable(void *arg)

{

	u64 val;



	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))

		return 0;



	rdmsrq(MSR_AMD64_SYSCFG, val);



	val |= MSR_AMD64_SYSCFG_MFDM;



	wrmsrq(MSR_AMD64_SYSCFG, val);

		return;



	return 0;

	msr_set_bit(MSR_AMD64_SYSCFG, MSR_AMD64_SYSCFG_MFDM_BIT);

}



static __init void mfd_enable(void *arg)

{

	__mfd_enable(smp_processor_id());

}



static int __snp_enable(unsigned int cpu)

static __init void snp_enable(void *arg)

{

	u64 val;



	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))

		return 0;

		return;



	rdmsrq(MSR_AMD64_SYSCFG, val);
@@ -164,13 +151,6 @@ static int __snp_enable(unsigned int cpu) 
	val |= MSR_AMD64_SYSCFG_SNP_VMPL_EN;



	wrmsrq(MSR_AMD64_SYSCFG, val);



	return 0;

}



static __init void snp_enable(void *arg)

{

	__snp_enable(smp_processor_id());

}



static void __init __snp_fixup_e820_tables(u64 pa)
@@ -553,8 +533,6 @@ int __init snp_rmptable_init(void) 
	on_each_cpu(snp_enable, NULL, 1);



skip_enable:

	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/rmptable_init:online", __snp_enable, NULL);



	/*

	 * Setting crash_kexec_post_notifiers to 'true' to ensure that SNP panic

	 * notifier is invoked to do SNP IOMMU shutdown before kdump.