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SubjectRe: [PATCH 2/2] arm:kvm remove len 8 for mmio read write buf
On 22/12/14 11:23, Peng Fan wrote:
> For arm 32 bit architecture, 8 bytes load/store operation in one instruction
> will not be generated by compiler.

Ever heard of lrdr/strd?

> And before invoke mmio_read_buf, there is a piece of code:
> "
> len = run->mmio.len;
> if (len > sizeof(unsigned long))
> return -EINVAL;
>
> data = mmio_read_buf(run->mmio.data, len);
> "
>
> This piece code also tells that len variable does not exceeds 4 bytes.
> So, remove 8 bytes assign in mmio_read_buf and mmio_write_buf.

NAK. This code is shared between arm and arm64. See commit f42798c.

M.

>
> Signed-off-by: Peng Fan <van.freenix@gmail.com>
> CC: Gleb Natapov <gleb@kernel.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Christoffer Dall <christoffer.dall@linaro.org>
> CC: Marc Zyngier <marc.zyngier@arm.com>
> CC: Russell King <linux@arm.linux.org.uk>
> ---
> arch/arm/kvm/mmio.c | 10 ----------
> 1 file changed, 10 deletions(-)
>
> diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
> index 4cb5a93..953a819 100644
> --- a/arch/arm/kvm/mmio.c
> +++ b/arch/arm/kvm/mmio.c
> @@ -30,7 +30,6 @@ static void mmio_write_buf(char *buf, unsigned int len, unsigned long data)
> u8 byte;
> u16 hword;
> u32 word;
> - u64 dword;
> } tmp;
>
> switch (len) {
> @@ -46,10 +45,6 @@ static void mmio_write_buf(char *buf, unsigned int len, unsigned long data)
> tmp.word = data;
> datap = &tmp.word;
> break;
> - case 8:
> - tmp.dword = data;
> - datap = &tmp.dword;
> - break;
> }
>
> memcpy(buf, datap, len);
> @@ -61,7 +56,6 @@ static unsigned long mmio_read_buf(char *buf, unsigned int len)
> union {
> u16 hword;
> u32 word;
> - u64 dword;
> } tmp;
>
> switch (len) {
> @@ -76,10 +70,6 @@ static unsigned long mmio_read_buf(char *buf, unsigned int len)
> memcpy(&tmp.word, buf, len);
> data = tmp.word;
> break;
> - case 8:
> - memcpy(&tmp.dword, buf, len);
> - data = tmp.dword;
> - break;
> }
>
> return data;
>


--
Jazz is not dead. It just smells funny...


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