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From: Andrew Jones <ajones@ventanamicro.com>
To: Atish Kumar Patra <atishp@rivosinc.com>
Cc: linux-kernel@vger.kernel.org, Anup Patel <anup@brainfault.org>,
	Atish Patra <atishp@atishpatra.org>, Guo Ren <guoren@kernel.org>,
	kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	Mark Rutland <mark.rutland@arm.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Sergey Matyukevich <sergey.matyukevich@syntacore.com>,
	Eric Lin <eric.lin@sifive.com>, Will Deacon <will@kernel.org>
Subject: Re: [PATCH v2 04/11] RISC-V: KVM: Modify SBI extension handler to return SBI error code
Date: Fri, 13 Jan 2023 08:42:04 +0100	[thread overview]
Message-ID: <20230113074204.p3wmeer2o3penunt@orel> (raw)
In-Reply-To: <CAHBxVyEyMdk+vQ5wTgOF56UJs-zLtkVixDxXquTjoLyV6Vj21Q@mail.gmail.com>

On Thu, Jan 12, 2023 at 10:47:13AM -0800, Atish Kumar Patra wrote:
> On Thu, Jan 12, 2023 at 3:04 AM Andrew Jones <ajones@ventanamicro.com> wrote:
> >
> > On Thu, Dec 15, 2022 at 09:00:39AM -0800, Atish Patra wrote:
...
> > > +      * and forwards the error to the userspace.
> > > +      */
> > > +     if (ret < 0) {
> > > +             next_sepc = false;
> > > +             goto ecall_done;
> > > +     }
> >
> > Shouldn't this ret < 0 check go above the "Handle special error cases..."
> > block?
> >
> 
> Why ? I thought if an extension handler has both utrap updated and
> returns an error,
> user space redirection should take precedence. Let me know if it is wrong.

My thinking was that utrap cannot be trusted if the handler returned an
error. The handler may not even have had a chance to set it before hitting
the error condition. IOW, we should check 'ret' right after the handler
call. If it's < 0, then from the caller's perspective the handler didn't
execute due to a KVM failure and it should be reported to userspace.

Thanks,
drew

  reply	other threads:[~2023-01-13  7:42 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-15 17:00 [PATCH v2 00/11] KVM perf support Atish Patra
2022-12-15 17:00 ` [PATCH v2 01/11] RISC-V: Define helper functions expose hpm counter width and count Atish Patra
2023-01-12 10:06   ` Andrew Jones
2023-01-12 18:18     ` Atish Kumar Patra
2023-01-13  7:22       ` Andrew Jones
2023-01-24 20:41         ` Atish Patra
2022-12-15 17:00 ` [PATCH v2 02/11] RISC-V: KVM: Define a probe function for SBI extension data structures Atish Patra
2023-01-12 10:21   ` Andrew Jones
2023-01-12 18:19     ` Atish Kumar Patra
2022-12-15 17:00 ` [PATCH v2 03/11] RISC-V: KVM: Return correct code for hsm stop function Atish Patra
2023-01-12 10:28   ` Andrew Jones
2023-01-12 18:25     ` Atish Kumar Patra
2023-01-13  7:25       ` Andrew Jones
2022-12-15 17:00 ` [PATCH v2 04/11] RISC-V: KVM: Modify SBI extension handler to return SBI error code Atish Patra
2023-01-12 11:04   ` Andrew Jones
2023-01-12 18:47     ` Atish Kumar Patra
2023-01-13  7:42       ` Andrew Jones [this message]
2022-12-15 17:00 ` [PATCH v2 05/11] RISC-V: KVM: Improve privilege mode filtering for perf Atish Patra
2022-12-15 20:17   ` Conor Dooley
2022-12-15 21:10     ` Atish Kumar Patra
2022-12-15 17:00 ` [PATCH v2 06/11] RISC-V: KVM: Add skeleton support " Atish Patra
2023-01-12 15:10   ` Andrew Jones
2023-01-12 18:09     ` Atish Kumar Patra
2022-12-15 17:00 ` [PATCH v2 07/11] RISC-V: KVM: Add SBI PMU extension support Atish Patra
2023-01-12 15:29   ` Andrew Jones
2023-01-12 18:04     ` Atish Kumar Patra
2022-12-15 17:00 ` [PATCH v2 08/11] RISC-V: KVM: Disable all hpmcounter access for VS/VU mode Atish Patra
2023-01-12 15:47   ` Andrew Jones
2022-12-15 17:00 ` [PATCH v2 09/11] RISC-V: KVM: Implement trap & emulate for hpmcounters Atish Patra
2023-01-13 11:47   ` Andrew Jones
2022-12-15 17:00 ` [PATCH v2 10/11] RISC-V: KVM: Implement perf support without sampling Atish Patra
2023-01-13 11:45   ` Andrew Jones
2023-01-23  7:23     ` Andrew Jones
2023-01-26  0:50     ` Atish Patra
2022-12-15 17:00 ` [PATCH v2 11/11] RISC-V: KVM: Implement firmware events Atish Patra
2023-01-13 12:08   ` Andrew Jones
2023-01-26  3:08     ` Atish Patra

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