From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
Jan Beulich <JBeulich@suse.com>
Cc: xen-devel@lists.xenproject.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
David Vrabel <david.vrabel@citrix.com>,
Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCH v3 07/32] xen/x86: fix arch_set_info_guest for HVM guests
Date: Mon, 3 Aug 2015 19:31:21 +0200 [thread overview]
Message-ID: <55BFA569.7050102@citrix.com> (raw)
In-Reply-To: <55BF9CE6.1030904@citrix.com>
El 03/08/15 a les 18.55, Andrew Cooper ha escrit:
> On 24/07/15 17:54, Roger Pau Monné wrote:
>>
>>>> struct vcpu_hvm_context {
>>>> /* 16bit fields of the strucutre will be used. */
>>>> #define _VCPUHVM_MODE_16B 0
>>>> #define VCPUHVM_MODE_16B (1<<_VCPUHVM_MODE_16B)
>>>> /* 32bit fields of the structure will be used. */
>>>> #define _VCPUHVM_MODE_32B 1
>>>> #define VCPUHVM_MODE_32B (1<<_VCPUHVM_MODE_32B)
>>>> /* 64bit fields of the structure will be used. */
>>>> #define _VCPUHVM_MODE_64B 2
>>>> #define VCPUHVM_MODE_64B (1<<_VCPUHVM_MODE_64B)
>>> As soon as we have three values here, a boolean flag approach
>>> doesn't make sense anymore.
>> Yes, taking into account that only _one_ of them can be used at the same
>> time.
>>
>> I have the feeling that we are over engineering this interface. IMHO we
>> should only allow the user to set the control registers, efer (on amd64)
>> and the GP registers. Segment selectors would be set by Xen to point to
>> a flat segment suitable for the mode the guest has selected. I think
>> that should be enough to get the guest OS into it's entry point, and
>> then it can do whatever it wants.
>>
>> If that's not suitable, then my second option would be to allow the
>> guest to set the base, limit and AR bytes of the selectors, but not load
>> a GDT.
>
> In an ideal world, it would be nice to pass enough state to be able to
> point eip at the idle loop and have everything JustWork. However, this
> makes a lot of assumptions about exactly which state the vcpu wants to
> set up, which might include MSRs as well.
>
> Therefore, an appropriate compromise is to be able to point eip at
> startup_cpu, running in the correct operating mode to avoid bouncing
> through trampolines.
IMHO, allowing OSes to jump straight into the idle loop is putting a
lot of burden in the Xen side of things. Also all OSes already contain
AP startup code, we should be able to hook into this code at a suitable
location, and that's what we should aim for.
>>From that point of view, the minimum quantity of state required is:
>
> CR{0,3,4}, EFER, cs/eip, ds, ss/esp, gdt{base,limit}. It would be
> natural to extend this to all the 8 base GPRs and the user segment
> selectors. (Note that EFER is needed even for 32bit paged entries if NX
> is set in the pagetables.)
Extending this to the rest of the GPR is needed for Linux to boot. The
AP startup code of PVH Linux places the cpu id in a GPR for the boot
stub to find it:
http://lxr.free-electrons.com/source/arch/x86/xen/smp.c#L420
>
> In addition, a hint to Xen as to the eventual mode so it can widen its
> reads to start with rather than attempting to reverse engineer the
> operating mode and rereading half the structure later.
>
> Specifying the gdt{base,limit} will require Xen to read the GDT to set
> up the entry attributes for the segment, as simply setting the selector
> is insufficient. A complicating factor is that VT-x and SVM have
> different representations for access rights. (For migration, VT-x's
> representation is mutated to match SVM.)
>
> I really undecided between suggesting a gdt{base,limit} and Xen reading
> the access rights in an unambiguous fashon, vs specifying the internals
> and avoiding any peeking into domain memory.
>
> It would be nice if the new cpus gs base could be set by the caller,
> which allows the new cpu straight access to its per-cpu data area (if gs
> is in use). This is not representable using the gdt method and would
> involve casing the GSBASE MSR if we were to go down the strict
> architectural route.
IMHO, this is out of the scope and I would rather allow the caller to
set the internal (cached) part of the segment selectors.
> Therefore, I am leaning slightly towards the specify the internals side
> of things, which removes some complexity from the Xen side of the hypercall.
I've updated the proposed structure, so now it looks like:
(I still need to figure out how to order the bits in the access rights
(_ar) fields.)
struct vcpu_hvm_x86_16 {
uint16_t ax;
uint16_t cx;
uint16_t dx;
uint16_t bx;
uint16_t sp;
uint16_t bp;
uint16_t si;
uint16_t di;
uint16_t ip;
uint32_t cr[8];
uint32_t cs_base;
uint32_t ds_base;
uint32_t ss_base;
uint32_t cs_limit;
uint32_t ds_limit;
uint32_t ss_limit;
uint16_t cs_ar;
uint16_t ds_ar;
uint16_t ss_ar;
};
struct vcpu_hvm_x86_32 {
uint32_t eax;
uint32_t ecx;
uint32_t edx;
uint32_t ebx;
uint32_t esp;
uint32_t ebp;
uint32_t esi;
uint32_t edi;
uint32_t eip;
uint32_t cr[8];
uint64_t efer;
uint32_t cs_base;
uint32_t ds_base;
uint32_t ss_base;
uint32_t cs_limit;
uint32_t ds_limit;
uint32_t ss_limit;
uint16_t cs_ar;
uint16_t ds_ar;
uint16_t ss_ar;
};
struct vcpu_hvm_x86_64 {
uint64_t rax;
uint64_t rcx;
uint64_t rdx;
uint64_t rbx;
uint64_t rsp;
uint64_t rbp;
uint64_t rsi;
uint64_t rdi;
uint64_t r8;
uint64_t r9;
uint64_t r10;
uint64_t r11;
uint64_t r12;
uint64_t r13;
uint64_t r14;
uint64_t r15;
uint64_t rip;
uint64_t cr[8];
uint64_t efer;
};
typedef enum {
VCPU_HVM_MODE_16B, /* 16bit fields of the structure will be used. */
VCPU_HVM_MODE_32B, /* 32bit fields of the structure will be used. */
VCPU_HVM_MODE_64B, /* 64bit fields of the structure will be used. */
} vcpu_hvm_mode_t;
struct vcpu_hvm_context {
vcpu_hvm_mode_t mode;
/* CPU registers. */
union {
struct vcpu_hvm_x86_16 x86_16;
struct vcpu_hvm_x86_32 x86_32;
struct vcpu_hvm_x86_64 x86_64;
};
};
typedef struct vcpu_hvm_context vcpu_hvm_context_t;
DEFINE_XEN_GUEST_HANDLE(vcpu_hvm_context_t);
next prev parent reply other threads:[~2015-08-03 17:31 UTC|newest]
Thread overview: 121+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-03 11:34 [PATCH v3 00/32] Introduce HVM without dm and new boot ABI Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 01/32] libxc: split x86 HVM setup_guest into smaller logical functions Roger Pau Monne
2015-07-06 10:45 ` Andrew Cooper
2015-07-28 11:22 ` Wei Liu
2015-07-03 11:34 ` [PATCH v3 02/32] libxc: unify xc_dom_p2m_{host/guest} Roger Pau Monne
2015-07-06 10:49 ` Andrew Cooper
2015-07-28 11:22 ` Wei Liu
2015-07-03 11:34 ` [PATCH v3 03/32] libxc: introduce the notion of a container type Roger Pau Monne
2015-07-06 12:01 ` Andrew Cooper
2015-07-28 11:22 ` Wei Liu
2015-07-03 11:34 ` [PATCH v3 04/32] libxc: introduce a domain loader for HVM guest firmware Roger Pau Monne
2015-07-06 12:11 ` Andrew Cooper
2015-07-28 11:22 ` Wei Liu
2015-07-03 11:34 ` [PATCH v3 05/32] libxc: make arch_setup_meminit a xc_dom_arch hook Roger Pau Monne
2015-07-06 12:23 ` Andrew Cooper
2015-07-27 10:40 ` Roger Pau Monné
2015-07-28 11:22 ` Wei Liu
2015-07-03 11:34 ` [PATCH v3 06/32] libxc: make arch_setup_boot{init/late} xc_dom_arch hooks Roger Pau Monne
2015-07-06 12:27 ` Andrew Cooper
2015-07-28 11:22 ` Wei Liu
2015-07-03 11:34 ` [PATCH v3 07/32] xen/x86: fix arch_set_info_guest for HVM guests Roger Pau Monne
2015-07-06 12:58 ` Andrew Cooper
2015-07-23 10:14 ` Roger Pau Monné
2015-07-10 18:39 ` Konrad Rzeszutek Wilk
2015-07-10 18:47 ` Konrad Rzeszutek Wilk
2015-07-23 10:17 ` Roger Pau Monné
2015-07-13 14:01 ` Jan Beulich
2015-07-23 10:25 ` Roger Pau Monné
2015-07-23 11:29 ` Jan Beulich
2015-07-23 11:41 ` Ian Campbell
2015-07-23 15:10 ` Roger Pau Monné
2015-07-23 15:32 ` Jan Beulich
2015-07-23 15:48 ` Roger Pau Monné
2015-07-23 15:58 ` Jan Beulich
2015-07-23 16:00 ` Ian Campbell
2015-07-23 16:15 ` Andrew Cooper
2015-07-23 16:19 ` Jan Beulich
2015-07-23 16:49 ` Andrew Cooper
2015-07-23 17:06 ` Roger Pau Monné
2015-07-23 16:56 ` Roger Pau Monné
2015-07-23 17:12 ` Andrew Cooper
2015-07-24 8:22 ` Jan Beulich
2015-07-24 9:59 ` Roger Pau Monné
2015-07-24 10:46 ` Jan Beulich
2015-07-24 12:11 ` Roger Pau Monné
2015-07-24 12:44 ` Jan Beulich
2015-07-24 15:26 ` Roger Pau Monné
2015-07-24 15:49 ` Jan Beulich
2015-07-24 16:54 ` Roger Pau Monné
2015-07-24 17:36 ` Konrad Rzeszutek Wilk
2015-07-27 11:55 ` Roger Pau Monné
2015-08-03 16:55 ` Andrew Cooper
2015-08-03 17:31 ` Roger Pau Monné [this message]
2015-08-04 18:08 ` Andrew Cooper
2015-08-05 9:53 ` Roger Pau Monné
2015-08-05 15:39 ` Andrew Cooper
2015-08-05 16:40 ` Roger Pau Monné
2015-08-05 16:46 ` Andrew Cooper
2015-08-05 17:11 ` Roger Pau Monné
2015-08-05 19:00 ` Andrew Cooper
2015-08-07 12:15 ` Tim Deegan
2015-08-11 7:26 ` Jan Beulich
2015-07-24 11:11 ` Andrew Cooper
2015-07-24 11:28 ` Ian Campbell
2015-07-24 11:49 ` Jan Beulich
2015-07-24 11:46 ` Jan Beulich
2015-07-24 11:49 ` Roger Pau Monné
2015-07-24 12:41 ` Jan Beulich
2015-07-24 15:28 ` Roger Pau Monné
2015-07-03 11:34 ` [PATCH v3 08/32] libxc: introduce a xc_dom_arch for hvm-3.0-x86_32 guests Roger Pau Monne
2015-07-06 13:40 ` Andrew Cooper
2015-07-03 11:34 ` [PATCH v3 09/32] libxl: switch HVM domain building to use xc_dom_* helpers Roger Pau Monne
2015-07-28 11:22 ` Wei Liu
2015-07-28 14:26 ` Roger Pau Monné
2015-07-28 14:29 ` Wei Liu
2015-07-03 11:34 ` [PATCH v3 10/32] libxc: remove dead HVM building code Roger Pau Monne
2015-07-06 13:46 ` Andrew Cooper
2015-07-23 10:27 ` Roger Pau Monné
2015-07-03 11:34 ` [PATCH v3 11/32] xen/x86: add bitmap of enabled emulated devices Roger Pau Monne
2015-07-06 14:10 ` Andrew Cooper
2015-07-07 7:26 ` Jan Beulich
2015-07-23 10:29 ` Roger Pau Monné
2015-07-03 11:34 ` [PATCH v3 12/32] xen/x86: allow disabling the emulated local apic Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 13/32] xen/x86: allow disabling the emulated HPET Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 14/32] xen/x86: allow disabling the pmtimer Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 15/32] xen/x86: allow disabling the emulated RTC Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 16/32] xen/x86: allow disabling the emulated IO APIC Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 17/32] xen/x86: allow disabling the emulated PIC Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 18/32] xen/x86: allow disabling the emulated pmu Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 19/32] xen/x86: allow disabling the emulated VGA Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 20/32] xen/x86: allow disabling the emulated IOMMU Roger Pau Monne
2015-07-03 11:34 ` [PATCH v3 21/32] xen/x86: allow disabling all emulated devices inside of Xen Roger Pau Monne
2015-07-03 11:35 ` [PATCH v3 22/32] elfnotes: intorduce a new PHYS_ENTRY elfnote Roger Pau Monne
2015-07-03 11:35 ` [PATCH v3 23/32] libxc: allow creating domains without emulated devices Roger Pau Monne
2015-07-28 11:22 ` Wei Liu
2015-07-03 11:35 ` [PATCH v3 24/32] xen: allow HVM guests to use XENMEM_memory_map Roger Pau Monne
2015-07-03 11:35 ` [PATCH v3 25/32] xen/x86: allow HVM guests to use hypercalls to bring up vCPUs Roger Pau Monne
2015-07-03 11:35 ` [PATCH v3 26/32] xenconsole: try to attach to PV console if HVM fails Roger Pau Monne
2015-07-14 13:46 ` Stefano Stabellini
2015-07-23 10:30 ` Roger Pau Monné
2015-07-03 11:35 ` [PATCH v3 27/32] libxc: change the position of the special pages Roger Pau Monne
2015-07-03 15:36 ` Roger Pau Monné
2015-07-10 19:06 ` Konrad Rzeszutek Wilk
2015-07-23 10:42 ` Roger Pau Monné
2015-07-03 11:35 ` [PATCH v3 28/32] libxc/xen: introduce HVM_PARAM_CMDLINE_PFN Roger Pau Monne
2015-07-03 11:35 ` [PATCH v3 29/32] libxc/xen: introduce HVM_PARAM_FIRST_FREE_PFN Roger Pau Monne
2015-07-10 19:05 ` Konrad Rzeszutek Wilk
2015-07-23 10:46 ` Roger Pau Monné
2015-07-03 11:35 ` [PATCH v3 30/32] libxc/xen: introduce HVM_PARAM_MODLIST_PFN Roger Pau Monne
2015-07-03 11:35 ` [PATCH v3 31/32] libxc: switch xc_dom_elfloader to be used with HVMlite domains Roger Pau Monne
2015-07-10 19:07 ` Konrad Rzeszutek Wilk
2015-07-23 10:48 ` Roger Pau Monné
2015-07-03 11:35 ` [PATCH v3 32/32] libxl: allow the creation of HVM domains without a device model Roger Pau Monne
2015-07-28 11:22 ` Wei Liu
2015-07-29 14:43 ` Roger Pau Monné
2015-07-29 14:50 ` Wei Liu
2015-07-29 14:58 ` Andrew Cooper
2015-07-03 16:19 ` [PATCH v3 00/32] Introduce HVM without dm and new boot ABI David Vrabel
2015-07-03 16:36 ` Roger Pau Monné
2015-07-10 17:44 ` Konrad Rzeszutek Wilk
2015-07-10 18:01 ` Konrad Rzeszutek Wilk
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