From: Jan Beulich <jbeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 4/4] x86/boot: Size the boot/directmap mappings dynamically
Date: Tue, 14 Jan 2020 18:02:13 +0100 [thread overview]
Message-ID: <c8b1dd46-5873-aec8-de72-402aa74727f2@suse.com> (raw)
In-Reply-To: <20200113175020.32730-6-andrew.cooper3@citrix.com>
On 13.01.2020 18:50, Andrew Cooper wrote:
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -687,14 +687,19 @@ trampoline_setup:
> * handling/walking), and identity map Xen into bootmap (needed for
> * the transition into long mode), using 2M superpages.
> */
> - lea sym_esi(start),%ebx
> - lea (1<<L2_PAGETABLE_SHIFT)*7+(PAGE_HYPERVISOR_RWX|_PAGE_PSE)(%ebx),%eax
> - shr $(L2_PAGETABLE_SHIFT-3),%ebx
> - mov $8,%ecx
> -1: mov %eax,sym_fs(l2_bootmap)-8(%ebx,%ecx,8)
> - mov %eax,sym_fs(l2_directmap)-8(%ebx,%ecx,8)
> - sub $(1<<L2_PAGETABLE_SHIFT),%eax
> - loop 1b
> + lea sym_esi(_start), %ecx
> + lea -1 + sym_esi(_end), %edx
This looks pretty odd - does
lea sym_esi(_end) - 1, %edx
not work?
> + lea _PAGE_PSE + PAGE_HYPERVISOR_RWX(%ecx), %eax /* PTE to write. */
> + shr $L2_PAGETABLE_SHIFT, %ecx /* First slot to write. */
> + shr $L2_PAGETABLE_SHIFT, %edx /* Final slot to write. */
> +
> +1: mov %eax, sym_offs(l2_bootmap) (%esi, %ecx, 8)
> + mov %eax, sym_offs(l2_directmap)(%esi, %ecx, 8)
I guess I could have noticed this on the previous patch already:
This would look better as
1: mov %eax, sym_esi(l2_bootmap, %ecx, 8)
mov %eax, sym_esi(l2_directmap, %ecx, 8)
Can sym_esi() perhaps be made
#define sym_esi(sym, extra...) sym_offs(sym)(%esi, ## extra)
?
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -384,6 +384,3 @@ ASSERT((trampoline_end - trampoline_start) < TRAMPOLINE_SPACE - MBI_SPACE_MIN,
> "not enough room for trampoline and mbi data")
> ASSERT((wakeup_stack - wakeup_stack_start) >= WAKEUP_STACK_MIN,
> "wakeup stack too small")
> -
> -/* Plenty of boot code assumes that Xen isn't larger than 16M. */
> -ASSERT(_end - _start <= MB(16), "Xen too large for early-boot assumptions")
Following your reply to the cover letter, this can't be dropped just yet.
Even when that remaining issue got addressed, I think it would be better
to keep it, altering the bound to GB(1).
Jan
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next prev parent reply other threads:[~2020-01-14 17:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-13 17:50 [Xen-devel] [PATCH 0/4] x86: Remove 16M total-size restriction Andrew Cooper
2020-01-13 17:50 ` [Xen-devel] [PATCH 1/4] x86/boot: Rename l?_identmap to l?_directmap Andrew Cooper
2020-01-14 16:16 ` Jan Beulich
2020-01-13 17:50 ` [Xen-devel] [PATCH 2/4] x86/page: Remove bifrucated PAGE_HYPERVISOR constant Andrew Cooper
2020-01-13 17:50 ` [Xen-devel] [PATCH 2/4] x86/page: Remove bifurcated " Andrew Cooper
2020-01-14 16:25 ` Jan Beulich
2020-01-15 12:53 ` Andrew Cooper
2020-01-15 13:07 ` Jan Beulich
2020-01-15 14:08 ` [Xen-devel] [PATCH v2 " Andrew Cooper
2020-01-16 9:46 ` Jan Beulich
2020-01-13 17:50 ` [Xen-devel] [PATCH 3/4] x86/boot: Create the l2_xenmap[] mappings dynamically Andrew Cooper
2020-01-14 16:45 ` Jan Beulich
2020-01-14 19:31 ` Andrew Cooper
2020-01-15 9:23 ` Jan Beulich
2020-01-16 19:41 ` Andrew Cooper
2020-01-13 17:50 ` [Xen-devel] [PATCH 4/4] x86/boot: Size the boot/directmap " Andrew Cooper
2020-01-14 17:02 ` Jan Beulich [this message]
2020-01-14 17:27 ` Andrew Cooper
2020-01-15 9:40 ` Jan Beulich
2020-01-15 10:21 ` Jan Beulich
2020-01-14 13:03 ` [Xen-devel] [PATCH 0/4] x86: Remove 16M total-size restriction Andrew Cooper
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