linux-kernel - [RFC 18/48] RISC-V: KVM: Skip TLB management for TVMs

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Date:   Wed, 19 Apr 2023 15:16:46 -0700
From:   Atish Patra <atishp@...osinc.com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atishp@...osinc.com>, Alexandre Ghiti <alex@...ti.fr>,
        Andrew Jones <ajones@...tanamicro.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Björn Töpel <bjorn@...osinc.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-coco@...ts.linux.dev, Dylan Reid <dylan@...osinc.com>,
        abrestic@...osinc.com, Samuel Ortiz <sameo@...osinc.com>,
        Christoph Hellwig <hch@...radead.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guo Ren <guoren@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
        Jiri Slaby <jirislaby@...nel.org>,
        kvm-riscv@...ts.infradead.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rajnesh Kanwal <rkanwal@...osinc.com>,
        Uladzislau Rezki <urezki@...il.com>
Subject: [RFC 18/48] RISC-V: KVM: Skip TLB management for TVMs

TSM manages the tlb entries for the TVMs. Thus, host can ignore
all the hfence requests or tlb updates for confidential guests.
Most of the hfence requests happen through vcpu requests which
are skipped for TVMs. Thus, we just need to take care of the
invocation from tlb management here.

Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 arch/riscv/kvm/tlb.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kvm/tlb.c b/arch/riscv/kvm/tlb.c
index dff37b57..b007c02 100644
--- a/arch/riscv/kvm/tlb.c
+++ b/arch/riscv/kvm/tlb.c
@@ -15,6 +15,7 @@
 #include <asm/hwcap.h>
 #include <asm/insn-def.h>
 #include <asm/kvm_nacl.h>
+#include <asm/kvm_cove.h>
 
 #define has_svinval()	riscv_has_extension_unlikely(RISCV_ISA_EXT_SVINVAL)
 
@@ -72,6 +73,14 @@ void kvm_riscv_local_hfence_gvma_gpa(gpa_t gpa, gpa_t gpsz,
 
 void kvm_riscv_local_hfence_gvma_all(void)
 {
+	/* For TVMs, TSM will take care of hfence.
+	 * TODO: We can't skip unconditionally if cove is enabled
+	 * as the host may be running in HS-mode and need to issue hfence
+	 * for legacy VMs.
+	 */
+	if (kvm_riscv_cove_enabled())
+		return;
+
 	asm volatile(HFENCE_GVMA(zero, zero) : : : "memory");
 }
 
@@ -160,7 +169,7 @@ void kvm_riscv_local_tlb_sanitize(struct kvm_vcpu *vcpu)
 {
 	unsigned long vmid;
 
-	if (!kvm_riscv_gstage_vmid_bits() ||
+	if (is_cove_vcpu(vcpu) || !kvm_riscv_gstage_vmid_bits() ||
 	    vcpu->arch.last_exit_cpu == vcpu->cpu)
 		return;
 
-- 
2.25.1