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KVM: RISC-V: SBI FWFT: Add optional init() callback for hardware probing

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Add an optional init() callback to separate one-time hardware probing
from runtime availability checks. For pointer masking, this allows
probing supported PMM lengths during initialization while checking ISA
extension availability at runtime.

Fix try_to_set_pmm() to restore the previous HENVCFG.PMM value after
probing, preventing side effects from hardware detection. Add preemption
protection to ensure CSR probe sequences complete atomically on the same
CPU.

Fixes: 6f576fc0ae ("RISC-V: KVM: Add support for SBI_FWFT_POINTER_MASKING_PMLEN")
Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260601-kvm-get_reg_list-v2-v5-2-415d08a2813b@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Yong-Xuan Wang 2026-06-01 03:26:23 -07:00 committed by Anup Patel
parent 63224b0274
commit 86957e5b4b
1 changed files with 29 additions and 4 deletions
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33
arch/riscv/kvm/vcpu_sbi_fwft.c
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@ -35,6 +35,16 @@ struct kvm_sbi_fwft_feature {
*/
bool (*supported)(struct kvm_vcpu *vcpu);
/**
* @init: Probe and initialize the feature on the vcpu
*
* This callback is optional. If provided, it will be called during
* vcpu initialization to probe the feature availability and perform
* any necessary initialization. Returns true if the feature is supported
* and initialized successfully, false otherwise.
*/
bool (*init)(struct kvm_vcpu *vcpu);
/**
* @reset: Reset the feature value irrespective whether feature is supported or not
*
@ -131,19 +141,30 @@ static long kvm_sbi_fwft_get_misaligned_delegation(struct kvm_vcpu *vcpu,
static bool try_to_set_pmm(unsigned long value)
{
unsigned long prev;
bool ret;
prev = csr_read_clear(CSR_HENVCFG, ENVCFG_PMM);
csr_set(CSR_HENVCFG, value);
return (csr_read_clear(CSR_HENVCFG, ENVCFG_PMM) & ENVCFG_PMM) == value;
ret = (csr_read_clear(CSR_HENVCFG, ENVCFG_PMM) & ENVCFG_PMM) == value;
csr_write(CSR_HENVCFG, prev);
return ret;
}
static bool kvm_sbi_fwft_pointer_masking_pmlen_supported(struct kvm_vcpu *vcpu)
{
return riscv_isa_extension_available(vcpu->arch.isa, SMNPM);
}
static bool kvm_sbi_fwft_pointer_masking_pmlen_init(struct kvm_vcpu *vcpu)
{
struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
if (!riscv_isa_extension_available(vcpu->arch.isa, SMNPM))
return false;
preempt_disable();
fwft->have_vs_pmlen_7 = try_to_set_pmm(ENVCFG_PMM_PMLEN_7);
fwft->have_vs_pmlen_16 = try_to_set_pmm(ENVCFG_PMM_PMLEN_16);
preempt_enable();
return fwft->have_vs_pmlen_7 || fwft->have_vs_pmlen_16;
}
@ -231,6 +252,7 @@ static const struct kvm_sbi_fwft_feature features[] = {
.first_reg_num = offsetof(struct kvm_riscv_sbi_fwft, pointer_masking.enable) /
sizeof(unsigned long),
.supported = kvm_sbi_fwft_pointer_masking_pmlen_supported,
.init = kvm_sbi_fwft_pointer_masking_pmlen_init,
.reset = kvm_sbi_fwft_reset_pointer_masking_pmlen,
.set = kvm_sbi_fwft_set_pointer_masking_pmlen,
.get = kvm_sbi_fwft_get_pointer_masking_pmlen,
@ -365,6 +387,9 @@ static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
else
conf->supported = true;
if (conf->supported && feature->init)
conf->supported = feature->init(vcpu);
conf->enabled = conf->supported;
conf->feature = feature;
}