Re: [PING PATCH v2] linux-user: Passthrough MADV_DONTNEED for certain file mappings

From: Richard Henderson <richard.henderson@linaro.org>
To: Ilya Leoshkevich <iii@linux.ibm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Laurent Vivier <laurent@vivier.eu>
Cc: qemu-devel@nongnu.org, Christian Borntraeger <borntraeger@linux.ibm.com>
Subject: Re: [PING PATCH v2] linux-user: Passthrough MADV_DONTNEED for certain file mappings
Date: Mon, 5 Sep 2022 19:14:32 +0100	[thread overview]
Message-ID: <ccf44208-d67c-f14d-dac3-f7a910309877@linaro.org> (raw)
In-Reply-To: <af00707e90837bfbdf7febae1d3327307948dcd7.camel@linux.ibm.com>

On 9/1/22 09:45, Ilya Leoshkevich wrote:
>> +/*
>> + * For linux-user, indicates that the page is mapped with the same
>> semantics
>> + * in both guest and host.
>> + */
>> +#define PAGE_PASSTHROUGH 0x0800

I would expect a change to PAGE_STICKY in accel/tcg/translate-all.c, so that this bit is 
preserved across mprotect.  Yes?

>> @@ -845,7 +861,7 @@ static bool
>> can_passthrough_madv_dontneed(abi_ulong start, abi_ulong end)
>>       }
>>   
>>       for (addr = start; addr < end; addr += TARGET_PAGE_SIZE) {
>> -        if (!(page_get_flags(addr) & PAGE_ANON)) {
>> +        if (!(page_get_flags(addr) & (PAGE_ANON |
>> PAGE_PASSTHROUGH))) {

Do you want both PAGE_ANON and PAGE_PASSTHROUGH?
If not, is PAGE_PASSTHOUGH is sufficient by itself, why check PAGE_ANON?

> I would like to ping this patch and two others that I used for
> debugging it:
> 
> [PATCH] linux-user: Fix stracing in-memory mmap arguments
> https://patchew.org/QEMU/20220630165901.2459135-1-iii@linux.ibm.com/

Queued to linux-user-next.

> [PATCH] linux-user: Implement stracing madvise()
> https://patchew.org/QEMU/20220725134440.172892-1-iii@linux.ibm.com/

There are many more MADV_* than just the 5 you list.

r~