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From: "Radim Krčmář" <rkrcmar@ventanamicro.com>
To: "Atish Patra" <atish.patra@linux.dev>,
	"Andrew Jones" <ajones@ventanamicro.com>
Cc: "Anup Patel" <anup@brainfault.org>,
	"Will Deacon" <will@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Mayuresh Chitale" <mchitale@ventanamicro.com>,
	<linux-riscv@lists.infradead.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <kvm@vger.kernel.org>,
	<kvm-riscv@lists.infradead.org>,
	"linux-riscv" <linux-riscv-bounces@lists.infradead.org>
Subject: Re: [PATCH v3 9/9] RISC-V: KVM: Upgrade the supported SBI version to 3.0
Date: Fri, 30 May 2025 13:09:43 +0200	[thread overview]
Message-ID: <DA9G60UI0ZLC.1KIWBXCTX0427@ventanamicro.com> (raw)
In-Reply-To: <2bac252c-883c-4f8a-9ae1-283660991520@linux.dev>

2025-05-29T11:44:38-07:00, Atish Patra <atish.patra@linux.dev>:
> On 5/29/25 3:24 AM, Radim Krčmář wrote:
>> I originally gave up on the idea, but I feel kinda bad for Drew now, so
>> trying again:
>
> I am sorry if some of my replies came across in the wrong way. That was 
> never
> the intention.

I didn't mean to accuse you, my apologies.  I agree with Drew's
positions, so to expand on a question that wasn't touched in his mail:

>> Even if userspace wants SBI for the M-mode interface, security minded
> This is probably a 3rd one ? Why we want M-mode interface in the user 
> space ?

It is about turning KVM into an ISA accelerator.

A guest thinks it is running in S/HS-mode.
The ecall instruction traps to M-mode.  RISC-V H extension doesn't
accelerate M-mode, so we have to emulate the trap in software.

The ISA doesn't say that M-mode means SBI.  We try really hard to have
SBI on all RISC-V, but I think KVM is taking it a bit too far.

We can discuss how best to describe SBI, so userspace can choose to
accelerate the M-mode in KVM, but I think that the ability to emulate
M-mode in userspace should be provided.

-- 
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  parent reply	other threads:[~2025-05-30 11:09 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-05-22 19:03 [PATCH v3 0/9] Add SBI v3.0 PMU enhancements Atish Patra
2025-05-22 19:03 ` [PATCH v3 1/9] drivers/perf: riscv: Add SBI v3.0 flag Atish Patra
2025-07-17 15:11   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 2/9] drivers/perf: riscv: Add raw event v2 support Atish Patra
2025-07-17 15:17   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 3/9] RISC-V: KVM: Add support for Raw event v2 Atish Patra
2025-07-17 15:18   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 4/9] drivers/perf: riscv: Implement PMU event info function Atish Patra
2025-07-18  4:32   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 5/9] drivers/perf: riscv: Export " Atish Patra
2025-07-18  4:39   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 6/9] KVM: Add a helper function to validate vcpu gpa range Atish Patra
2025-07-17 16:04   ` Anup Patel
2025-07-17 16:07   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 7/9] RISC-V: KVM: Use the new gpa range validate helper function Atish Patra
2025-07-18  4:40   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 8/9] RISC-V: KVM: Implement get event info function Atish Patra
2025-07-18  5:44   ` Anup Patel
2025-05-22 19:03 ` [PATCH v3 9/9] RISC-V: KVM: Upgrade the supported SBI version to 3.0 Atish Patra
2025-05-23 13:31   ` Radim Krčmář
2025-05-23 17:16     ` Atish Patra
2025-05-26  9:00       ` Radim Krčmář
2025-05-26 11:13         ` Andrew Jones
2025-05-28 14:16           ` Atish Patra
2025-05-28 15:09             ` Andrew Jones
2025-05-28 19:21               ` Atish Patra
2025-05-29  1:17                 ` Atish Patra
2025-05-29 10:24                 ` Radim Krčmář
2025-05-29 18:44                   ` Atish Patra
2025-05-29 19:14                     ` Andrew Jones
2025-05-30 11:45                       ` Anup Patel
2025-05-30 11:09                     ` Radim Krčmář [this message]
2025-05-30 19:29                       ` Atish Patra
2025-06-03 11:40                         ` Radim Krčmář
2025-06-04  0:29                           ` Atish Patra
2025-07-18  4:44   ` Anup Patel

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