From: Michael Tokarev <mjt@tls.msk.ru>
To: Alexander Graf <agraf@suse.de>
Cc: qemu-trivial <qemu-trivial@nongnu.org>,
QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [Qemu-trivial] [PATCH] x86: only allow real mode to access 32bit without LMA
Date: Sat, 07 Dec 2013 22:49:06 +0400 [thread overview]
Message-ID: <52A36DA2.4050508@msgid.tls.msk.ru> (raw)
In-Reply-To: <1386334344-24620-1-git-send-email-agraf@suse.de>
06.12.2013 16:52, Alexander Graf wrote:
> When we're running in non-64bit mode with qemu-system-x86_64 we can
> still end up with virtual addresses that are above the 32bit boundary
> if a segment offset is set up.
>
> GNU Hurd does exactly that. It sets the segment offset to 0x80000000 and
> puts its EIP value to 0x8xxxxxxx to access low memory.
>
> This doesn't hit us when we enable paging, as there we just mask away the
> unused bits. But with real mode, we assume that vaddr == paddr which is
> wrong in this case. Real hardware wraps the virtual address around at the
> 32bit boundary. So let's do the same.
>
> This fixes booting GNU Hurd in qemu-system-x86_64 for me.
Since i386 tcg code has no active maintainer and since this is a rather
simple change, I'll queue it up to trivial-patches.
Thank you!
/mjt
WARNING: multiple messages have this Message-ID (diff)
From: Michael Tokarev <mjt@tls.msk.ru>
To: Alexander Graf <agraf@suse.de>
Cc: qemu-trivial <qemu-trivial@nongnu.org>,
QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH] x86: only allow real mode to access 32bit without LMA
Date: Sat, 07 Dec 2013 22:49:06 +0400 [thread overview]
Message-ID: <52A36DA2.4050508@msgid.tls.msk.ru> (raw)
In-Reply-To: <1386334344-24620-1-git-send-email-agraf@suse.de>
06.12.2013 16:52, Alexander Graf wrote:
> When we're running in non-64bit mode with qemu-system-x86_64 we can
> still end up with virtual addresses that are above the 32bit boundary
> if a segment offset is set up.
>
> GNU Hurd does exactly that. It sets the segment offset to 0x80000000 and
> puts its EIP value to 0x8xxxxxxx to access low memory.
>
> This doesn't hit us when we enable paging, as there we just mask away the
> unused bits. But with real mode, we assume that vaddr == paddr which is
> wrong in this case. Real hardware wraps the virtual address around at the
> 32bit boundary. So let's do the same.
>
> This fixes booting GNU Hurd in qemu-system-x86_64 for me.
Since i386 tcg code has no active maintainer and since this is a rather
simple change, I'll queue it up to trivial-patches.
Thank you!
/mjt
next prev parent reply other threads:[~2013-12-07 18:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-06 12:52 [Qemu-devel] [PATCH] x86: only allow real mode to access 32bit without LMA Alexander Graf
2013-12-06 17:46 ` Richard Henderson
2013-12-06 18:48 ` Michael Tokarev
2013-12-06 18:57 ` Stefan Weil
2013-12-07 18:49 ` Michael Tokarev [this message]
2013-12-07 18:49 ` Michael Tokarev
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