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From: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
To: kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
	kvm@vger.kernel.org
Cc: anup@brainfault.org, atishp@atishpatra.org,
	ajones@ventanamicro.com,
	Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Subject: [PATCH v2 6/9] RISC-V: KVM: avoid EBUSY when writing same ISA val
Date: Tue,  1 Aug 2023 19:26:26 -0300	[thread overview]
Message-ID: <20230801222629.210929-7-dbarboza@ventanamicro.com> (raw)
In-Reply-To: <20230801222629.210929-1-dbarboza@ventanamicro.com>

kvm_riscv_vcpu_set_reg_config() will return -EBUSY if the ISA config reg
is being written after the VCPU ran at least once.

The same restriction isn't placed in kvm_riscv_vcpu_get_reg_config(), so
there's a chance that we'll -EBUSY out on an ISA config reg write even
if the userspace intended no changes to it.

We'll allow the same form of 'lazy writing' that registers such as
zicbom/zicboz_block_size supports: avoid erroring out if userspace made
no changes to the ISA config reg.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 arch/riscv/kvm/vcpu_onereg.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
index 67e1e9b0fd7e..b0821f75cc61 100644
--- a/arch/riscv/kvm/vcpu_onereg.c
+++ b/arch/riscv/kvm/vcpu_onereg.c
@@ -187,6 +187,13 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
 		if (fls(reg_val) >= RISCV_ISA_EXT_BASE)
 			return -EINVAL;
 
+		/*
+		 * Return early (i.e. do nothing) if reg_val is the same
+		 * value retrievable via kvm_riscv_vcpu_get_reg_config().
+		 */
+		if (reg_val == (vcpu->arch.isa[0] & KVM_RISCV_BASE_ISA_MASK))
+			break;
+
 		if (!vcpu->arch.ran_atleast_once) {
 			/* Ignore the enable/disable request for certain extensions */
 			for (i = 0; i < RISCV_ISA_EXT_BASE; i++) {
-- 
2.41.0


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  parent reply	other threads:[~2023-08-01 22:26 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-01 22:26 [PATCH v2 0/9] RISC-V: KVM: change get_reg/set_reg error codes Daniel Henrique Barboza
2023-08-01 22:26 ` [PATCH v2 1/9] RISC-V: KVM: return ENOENT in *_one_reg() when reg is unknown Daniel Henrique Barboza
2023-08-01 22:26 ` [PATCH v2 2/9] RISC-V: KVM: use ENOENT in *_one_reg() when extension is unavailable Daniel Henrique Barboza
2023-08-01 22:26 ` [PATCH v2 3/9] RISC-V: KVM: do not EOPNOTSUPP in set_one_reg() zicbo(m|z) Daniel Henrique Barboza
2023-08-01 22:26 ` [PATCH v2 4/9] RISC-V: KVM: do not EOPNOTSUPP in set KVM_REG_RISCV_TIMER_REG Daniel Henrique Barboza
2023-08-01 22:26 ` [PATCH v2 5/9] RISC-V: KVM: use EBUSY when !vcpu->arch.ran_atleast_once Daniel Henrique Barboza
2023-08-01 22:26 ` Daniel Henrique Barboza [this message]
2023-08-01 22:26 ` [PATCH v2 7/9] RISC-V: KVM: avoid EBUSY when writing the same machine ID val Daniel Henrique Barboza
2023-08-01 22:26 ` [PATCH v2 8/9] RISC-V: KVM: avoid EBUSY when writing the same isa_ext val Daniel Henrique Barboza
2023-08-01 22:26 ` [PATCH v2 9/9] docs: kvm: riscv: document EBUSY in KVM_SET_ONE_REG Daniel Henrique Barboza
2023-08-02  8:17   ` Andrew Jones
2023-08-02  9:04 ` [PATCH v2 0/9] RISC-V: KVM: change get_reg/set_reg error codes Andrew Jones
2023-08-02  9:06   ` Andrew Jones

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