Re: [PATCH kvmtool] arm64: pvtime: Use correct region size

From: Sebastian Ene <sebastianene@google.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: will@kernel.org, julien.thierry.kdev@gmail.com, maz@kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, pierre.gondois@arm.com
Subject: Re: [PATCH kvmtool] arm64: pvtime: Use correct region size
Date: Fri, 1 Jul 2022 15:29:40 +0000	[thread overview]
Message-ID: <Yr8S5E9Pdxr9QjRD@google.com> (raw)
In-Reply-To: <20220629103905.24480-1-alexandru.elisei@arm.com>

On Wed, Jun 29, 2022 at 11:39:05AM +0100, Alexandru Elisei wrote:
> pvtime uses ARM_PVTIME_BASE instead of ARM_PVTIME_SIZE for the size of the
> memory region given to the guest, which causes to the following error when
> creating a flash device (via the -F/--flash command line argument):
> 
>   Error: RAM (read-only) region [2000000-27fffff] would overlap RAM region [1020000-203ffff]
> 
> The read-only region represents the guest memory where the flash image is
> copied by kvmtool. The region starting at 0x102_0000 (ARM_PVTIME_BASE) is
> the pvtime region, which should be 64K in size. kvmtool erroneously creates
> the region to be ARM_PVTIME_BASE in size instead, and the last address
> becomes:
> 
> ARM_PVTIME_BASE + ARM_PVTIME_BASE - 1 = 0x102_0000 + 0x102_0000 - 1 = 0x203_ffff
> 
> which corresponds to the end of the region from the error message.
> 
> Do the right thing and make the pvtime memory region ARM_PVTIME_SIZE = 64K
> bytes, as it was intended.
> 
> Fixes: 7d4671e5d372 ("aarch64: Add stolen time support")
> Reported-by: Pierre Gondois <pierre.gondois@arm.com>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
>  arm/aarch64/pvtime.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 

Hi,

Thanks for fixing this.
Reviewed-by: Sebastian Ene <sebastianene@google.com>

> diff --git a/arm/aarch64/pvtime.c b/arm/aarch64/pvtime.c
> index a49cf3ed5478..2933ac7ca959 100644
> --- a/arm/aarch64/pvtime.c
> +++ b/arm/aarch64/pvtime.c
> @@ -14,15 +14,15 @@ static int pvtime__alloc_region(struct kvm *kvm)
>  	char *mem;
>  	int ret = 0;
>  
> -	mem = mmap(NULL, ARM_PVTIME_BASE, PROT_RW,
> +	mem = mmap(NULL, ARM_PVTIME_SIZE, PROT_RW,
>  		   MAP_ANON_NORESERVE, -1, 0);
>  	if (mem == MAP_FAILED)
>  		return -errno;
>  
>  	ret = kvm__register_ram(kvm, ARM_PVTIME_BASE,
> -				ARM_PVTIME_BASE, mem);
> +				ARM_PVTIME_SIZE, mem);
>  	if (ret) {
> -		munmap(mem, ARM_PVTIME_BASE);
> +		munmap(mem, ARM_PVTIME_SIZE);
>  		return ret;
>  	}
>  
> @@ -36,8 +36,8 @@ static int pvtime__teardown_region(struct kvm *kvm)
>  		return 0;
>  
>  	kvm__destroy_mem(kvm, ARM_PVTIME_BASE,
> -			 ARM_PVTIME_BASE, usr_mem);
> -	munmap(usr_mem, ARM_PVTIME_BASE);
> +			 ARM_PVTIME_SIZE, usr_mem);
> +	munmap(usr_mem, ARM_PVTIME_SIZE);
>  	usr_mem = NULL;
>  	return 0;
>  }
> -- 
> 2.36.1
> 

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