On Wed, 2022-05-25 at 16:57 +1200, Kai Huang wrote: > On Wed, 2022-05-25 at 16:47 +1200, Kai Huang wrote: > > On Fri, 2022-04-29 at 10:47 -0700, Dave Hansen wrote: > > > On 4/28/22 16:14, Kai Huang wrote: > > > > On Thu, 2022-04-28 at 07:06 -0700, Dave Hansen wrote: > > > > > On 4/27/22 17:15, Kai Huang wrote: > > > > > > > Couldn't we get rid of that comment if you did something like: > > > > > > > > > > > > > > ret = tdx_get_sysinfo(&tdx_cmr_array, &tdx_sysinfo); > > > > > > > > > > > > Yes will do. > > > > > > > > > > > > > and preferably make the variables function-local. > > > > > > > > > > > > 'tdx_sysinfo' will be used by KVM too. > > > > > > > > > > In other words, it's not a part of this series so I can't review whether > > > > > this statement is correct or whether there's a better way to hand this > > > > > information over to KVM. > > > > > > > > > > This (minor) nugget influencing the design also isn't even commented or > > > > > addressed in the changelog. > > > > > > > > TDSYSINFO_STRUCT is 1024B and CMR array is 512B, so I don't think it should be > > > > in the stack. I can change to use dynamic allocation at the beginning and free > > > > it at the end of the function. KVM support patches can change it to static > > > > variable in the file. > > > > > > 2k of stack is big, but it isn't a deal breaker for something that's not > > > nested anywhere and that's only called once in a pretty controlled > > > setting and not in interrupt context. I wouldn't cry about it. > > > > Hi Dave, > > > > I got below complaining when I use local variable for TDSYSINFO_STRUCT and CMR > > array: > > > > arch/x86/virt/vmx/tdx/tdx.c:383:1: warning: the frame size of 3072 bytes is > > larger than 1024 bytes [-Wframe-larger-than=] > > 383 | } > > > > So I don't think we can use local variable for them. I'll still use static > > variables to avoid dynamic allocation. In the commit message, I'll explain they > > are too big to put into the stack, and KVM will need to use TDSYSINFO_STRUCT > > reported by TDX module anyway. > > > > Let me know if you don't agree? > > Btw, CMR array alone can be put into the stack. It will never be used by KVM, > so I'll put CMR array as local variable, but keep tdx_sysinfo as static > variable. > Sorry for multiple emails about this. If I put CMR array to the stack, I still sometimes get the build warning. So will use static variables. Also, constructing TDMRs internally needs to use tdx_sysinfo (max_tdmrs, pamt_entry_size, max_rsvd_per_tdmr), so with static variable they don't need to be passed around as function arguments. -- Thanks, -Kai
